DNA from an ancient fossil reveals that Asians and Native Americans share a common ancestor, which lends further evidence to the theory that people from Asia were the first humans to set foot in the Americas. Researchers in China and Europe sequenced DNA extracted from a 40,000-year-old leg bone (pictured) found in the Tianyuan Cave site near Beijing.

At the time this individual was alive, modern humans co-existed with Neanderthals and Denisovans, two groups of early humans who diverged from Homo sapiens about 300-400 thousand years ago. Evolutionary biologists have already sequenced DNA from both Neanderthals and Denisovans, and discovered evidence that they were having children with modern humans (many modern European and Asian people have Neanderthal and Denisovan DNA). But until recently, we have known little about the genetic makeup of paleolithic humans who lived in Asia. What we do know is that as early as a million years ago, tool-using hominins called Homo erectus were living in Asia, and scientists have yearned to find out what happened to them.

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This bone doesn't give us any clues about what happened to Homo erectus in Asia, though we're pretty sure this hominin evolved into Homo sapiens in Africa. What we did find out is that early modern humans in Asia were very similar to Asians today. And they share enough DNA with Native Americans to confirm that it's very likely an ancient Asian people came to the Americas in reed boats that they piloted along the shoreline from the region that is China today all the way over to what are today the many nations on the Pacific side of the Americas.

Qiaomei Fu, Matthias Meyer and colleagues of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, extracted nuclear and mitochondrial DNA from a 40,000 year old leg bone . . . For their study the researchers were using new techniques that can identify ancient genetic material from an archaeological find even when large quantities of DNA from soil bacteria are present.

The researchers then reconstructed a genetic profile of the leg's owner. "This individual lived during an important evolutionary transition when early modern humans, who shared certain features with earlier forms such as Neanderthals, were replacing Neanderthals and Denisovans, who later became extinct", says Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology, who led the study . . .

The genetic profile reveals that this early modern human was related to the ancestors of many present-day Asians and Native Americans but had already diverged genetically from the ancestors of present-day Europeans. In addition, the Tianyuan individual did not carry a larger proportion of Neanderthal or Denisovan DNA than present-day people in the region. "More analyses of additional early modern humans across Eurasia will further refine our understanding of when and how modern humans spread across Europe and Asia", says Svante Pääbo.

We may never know what happened to Homo erectus in Asia, however, because these hominins lived too long ago for their DNA to have been preserved.